CA1129993A - Tape recorder having magnetically controlled tape tensioning - Google Patents

Abstract

47,488 ABSTRACT OF THE DISCLOSURE
A load survey tape recorder has a tape transport assembly including a supply spindle assembly having a magnetic brake and a take-up spindle assembly having a magnetic clutch. Substantially constant tensions are main-tained in a recording tape as it is driven between supply and take-up reels by the magnetic retarding forces Or the magnetic brake and by a variable magnetic drive coupling of the magnetic clutch. A non-magnetic spacer is placed in one or both of the magnetic coupling gaps of the brake and clutch for improved operation.

Description

~~~

47~48 TAPE RECORDER HAVING MAGNETICALLY
CONTROLLED TAPE TENSIONING

BACKGROUND O~ TH~'INVENTION
Fie'Id'o'f't'he'Invention:
~ his invention relates to tape recorders having tape transport assemblies for driving a recording tape past a record head and between two cartridge reels, and more particular:ly to such recorders includlng load survey mag-netic tape recorders having both magnetic brake and magnetic clutch'arrangements for maintainlng controlled and substan-tially constant tape tensions.
Description of the Prior Art:
The present invention is closely~related and is an improvement of a load survey type o~ magnetic tape recorder dlsclosed and claimed in U.S. Pat. No. 3~602~458, assigned to the assignee of this invention. The tape recorder is in-: tended for substantially contlnuous use in varying environ-mental condltions requiring highly reliable and rugged con-struction ~eatures. The tape transport assembly o~ the prior recorder utilizes a mechanical ~r~ction producing arrangement for providing a predetermined drag or retarding force on a take-up pulley assembly that receives the supply reel of a removable tape cartridge. The drag maintains a predetermined tension in the recording tape as lt is pulled - from the supply reel by a capstan assembly~of the recorder.
- The capstan is driven directly ~rom a constant speed drive motor. A take~up pulley assembly engages the take-up reel of the'cartridge and is drlven by a slipping spring belt which,' in turn, is driven by the capstan assembly. Sllppage betwe'en the sprlng belt and the' take-up pulley assembly 47~488 occurs to maintain a proper tape speed between the capstan and the take'-up reel as the tape is fed there~o. WhIle the a~orementioned recorder has been highly reliable and depend-able in extended service und.er sometimes di~ferent environ-mental conditions, reduction of the mechanical and frictional between the retarding and driving coupling o~ the supply pulley' and take-up pulley assemblies iæ desirable. The associated drag cord and spring belt drive tend to be some limitation to the li~e of the recorder and require maintenance 10 and cleaning o~ dirt and debris between the frictional .
''; engaging parts. Thus, rotational drag at the supply pulley assembly is desired to be better isolated-~rom a stationary retardation producing member and.the drivlng torque to the take-up pulley assembly iB de~ired ~o be transmitted acros~ : :
a more maintenance-~ree clutch inkerface. ~ .
In U.S. PatO No. 3,636,277, a video tape recorder requires a rotating magnetic head which has a rotation synchronized to the tape speed by a eddy current brake and hysteresis coupling arrangement. Further eddy current brake and hysteresis coupling arrangement~ are described ~or the capstan drive and guide rollers. In U.S. Pat. No. 3,967,790, a tape cartridge drive i~ disclosed hâving a capstan drive including a magnetic clutch which, ln turn, is coupled by gears to a take-up reel spindle. I~ U.S. Pat. No. 3,809,336, . a tape transport is described for bi-directional tape ~eed and take-up. The transport includes.a separate pair o~
clutche's an~ a separate magnetic.coupling, interconnectlng - each'of two tape spools and a drive motor. Symmetrical operation allows the spools to be'interchanged as take-up and supply spools operated at hi~h velocitles and subJect to .. ~

periodic stopping and starting. An air gap space in each magnetic coupling is exposed to small debrls and magnetic particles capable o~ accumulating therein to alter the torque and speed characteristics between the input and output o~ the coupllngs. U.S. Pat. No. 3,584,250 discloses a ~ilm pro~ec'tor take-up reel a~sembly rather than a.tape recorder having a capstan tape drlve arrangement. The take-: ,.~ . . .
up reel assembly includes a.magnetlc drlve coupling between a drive motor and the take-up reel. A cyllndrical cage carries' annular permanent magnets and a magnetically permeable ring axially spaced from the permanent magnets. The ring i5 ; ~ixed to a drive shaft of the take~up reel BO that the motor torque is transmitted across a magnetic air gap spaclng o~
the coupling. The magnekic coupllng air gap ls ad~ustable to ad~ust the maxlmum load transmitted by'.the coupllng.
. Upon fllm rewinding, the magnetic gap coupllng provldes magnetic breaking as fllm ls fed Or~ of the take-up spool.
The present invention'is dlrected to an lmproved tape drive arrangement ~or a unidirectional slow.speed and 20 continuously operating magnetic.tape recorder having a ..
magnetic brake at a supply spindle assembly and a magnetic clutch at the take up spindle assem~ly to provide reliable and consistent operation, and for controlling the.supply and take~up tape.tenslons and speeds wherein the magnetic olutch and brake arrangements.lnclude relatively mQvable parts including a magnetized part and~a permeable magnetic part separated by a protected non-magnet.ic gap space ~o prevent undesirea acc'umulations of.foreign ma~erial altering desired - rel'ati,~e rotatlon bet'ween the two magnet'ic coupllng parts.

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47,4 SUMMARY OF THE IN~NTION
In accordance with'the present invention, a load research magnetic tape recorder receives a two reel tape cartridge and includes a tape transport assembly including a capstan aæsembly, and supply and take-up spindle'assemblies.
The capstan and take-up spindle assemblies are driven by a ' drive motor so that magnetic tape is pulled from the supply ''' ~ reel past a magnetlc record head and onto the take-up reel ' ' of the cartridge. The capstan assembly is driven directly - -from a drive motor and engages the recording tape at a pinch roller to continuously dri~e the tape at low tape speeds.
The supply spindle assembly includes a two-part magnetic brake including statlonary and rotatlng par`ts with'one part being permanently magnetized and the other part being o~ a~ -soft or permeable magnetic material. The upper end of the rotating part includes pins ~or engaging the hub of a tape supply reel of the cartridge. Permanent magnet ~lux of the magnetized part ls directed into'khe permeable magnetic material of the other part so as to provlde'magnetic attrac-tion therebetween producing a predetermined drag ~orce on the supply reel as tape is pulled therefrom by the capstan.
A thin non-magnetic spacer washer separates the two'magnetic brake parts to protect the space therebetween from accumu-lating dlrt and debriæ and attraction of magnetic partlcles therebetween tending to alker the magnetic retarding e~fect thereof and producing damage to the brake parts. The spacer washer'pro~ldes'the non-magnetic air gap spacing and e~ects added frictlonal forces' adding to the magnetlc drag forces of the' brake.' The'capstan aæsembly includes a capstan shaft and f~ 3 1~'1, 1l8g a gear carried at the lower end thereof which is directly driven by a drive motor pinion gear. The motor provides constant rotating speed at the capstan. A positive driving and non-slipping drive belt connects the capstan assembly to the take'-up spindle assembly including a magnetic clutch.
The magnet'ic clutch has two parts including a clutch driving part driven by the non-slipping belt and a clutch driven - part carrying reel hub engaging pins for driving the take-up reel of the cartridge. One of the magnetic clutch parts is 10 permanently magnetized and the other is made of a soft or ''~
permeable magnetic material so that the d~lven clutch part is rotated by the drive motor via the magnetic coupling between the driven and driving parts of the` magnetic clutch. ~ -Controlled take-up reel speed is maintained by increasing , -slippage at the clutch so the magnetlc tape speed between the capstan and the take-up reel is substantially constant during the tape transporting operation. A spacer washer in , the air gap space of the magnetic cluteh prevents accumulation of fragments o~ interfering materials.
- Accordingly 9 supply and take-up recording tape tensions and speeds are controlled and maintained by an improved tape transport assembly including a suppl~ spindle assembly having a magnetic brake with a spacer member formed between the stationary and rotational parts thereof and ~urther including a take-up spindle assembly~havlng a mag-netic clutch with a spacer washer between the dri~en and driving parts thereor. The magnetic clutch and'the znagnetic brake'co'operatlvely maintain the des'ired and contr~lled tape tensions at a tape'supply reeI and controlled speed Yariations 3o at a tape ta~e-up reel so as to pre~ent undes~red tape . .

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3 47,11~8 transporting variations due to wear and contamlnatlon of the -related mo~ing parts and to produce increased reliable and maintenance free operation for continuous operation under varying and o~ten extreme environmental conditions. These and other advantages and features of the present invention will become apparent from the description of the drawings briefly described hereinafter.
BRIE~ DESCRIPTION OF THE ~RAWINGS
Flgure 1 is a front elevational view o~ a magnetic tape recorder made in accordance with this invention and an associated tape cartridge;
Fig. 2 is a cross-sectional view taken along the axis II-II in Fig. 1 and looking in the di~rection of the arrows with parts removed illustrating a tape transport assembly, Flg. 3 is an enlarged view showing o~ a take-up spindle assembly having a magnetic clutch included in the tape transport assembly shown in Fig. 2;
Fig. 4 is an enlarged view of a supply spindle assembly having a magnetic brake included in the tape trans-port assembly shown in Fig. 2;
Fig. 5 is a side elevational view w~th parts broken away of an alternative embodiment of a magnetic ~rake lncluding a magnetic coupling ad~usting arrangemenkj and Fig~ 6 is a cross-sectional view~taken along the axis VI-~I in Fig. 5 and lookIn~ in the direction of the arrow~.
DESC~IPTION OF THE PR~FEKRED ~MBODIMEN~S
Re~erring now to the drawings and more particularly 3o to Fig. l, there is shown an electric load research tape . " ' ~2 ~ ~ 3 7 47,488 recorder device 10 made in accordance with the present invention~ The recorder lO is typically used by electric power suppliers for elec-tric po~er usage surveys wherein meter pulses are recorded along with time interval pulse~ as disclosed ln UAS~ Pat. Nos. 374709470 and 3,913,12~, bo-th assigned to the assignee o~ this invention. The present invention is an improvement of the recorder dislosed and claimed in U.S. Pat. No. 3,602~458 also assigned to the assignee o~ this invention. The general arrangement and 1~ operation o~ the recorder lO is described in the last-named --patent except ~or the invention as ~escribed hereinO
Generally, the recorder 10 includes a frame 12 formed by a bottom plate 14, middle plate 16, and top plate 18, me frame 12 carries the tape transport assembly 20, shown in Fig. 2 and forming an important ~eature o~ the present invention, as described more fully hereinbelow. m e tape transport assembly 20 lncludes a cap~tan assembly 22 including a capstan sha~t 24 and a supply spi~dle assembly 26 and take-up spindle assembly 28~ Spring loaded pins 30 o~ the supply spindle assembly 26 and s~ring loaded pins 32 o~ the take-up splndle assembly 28 are exposed through openings of the middle plate 16. A magnetic record head 34 is carried on the middle plate 16 adJacent the capstan sha~t 24.
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~; A second main unit o~ the recorder 10 is a ~ape cartridge 38 which is substa~tially~identical as described and claimed ln the aforementioned Pat~ No~ 3,602~458 includ-~ ing a housing 40 having rotatably mounted therein a supply - reel 42 and take-up reel 44 carrying a predetermined length :

,.... . .

~7,488 of magnet:ic recording tape 46 extending between the reels 42 and 44 and around the outer surface'of a spring biased pinch roller 48. Upon inserting the cartridge 38 into the cart-ridge recelving area over' the middle plate 16, the pinch roller 48 ~iases the magnetic tape 46 again~t the capstan shaft 24 and posltlons the'tape against the record head 34.
As descrlbed in the aforementioned Pat. No. 3,602,458g the plns 30 and 32 engage the supply reel 42 and take-up reel 44, respectively. Controlled rokation of the reels is lU provided by the tape'transport assembly 20 of the present invention. . .
The tape transport assembly 20 is more clearly shown ln Flg. 2 whlch is a cross-sectional`view taken along the axis II-II of Fig. 1 and looking in the direction of t,he arrows. The operative parts of the cartridge 38 are shown ln Flg. 2 for a better understanding of the present lnven-tion with the cartrldge 38 being mounted in the operative and mounted position on the mid~le plate.16 with respect 'to the tape transport assembly 20 of the re¢order. 10. Accord-lngly, the reel 42 and reel`44 are shown with hub portions 42a and 44a thereof belng engaged by the,pins 30 and .32 of the spindle'assemblies 26 and 28 as described hereinabove.
The tape driving rotation o~ the capstan sha~t 24 is pro-vided at a gear 52 mounted on the bottom of.the ~haft 24 which meshes with a pinion gear 54.carried.by the shaft of a drive motor:56. The drive motor 56, being carried by the bottom plate.l4-, rotates at a predetermined substantlally low spee'~ to:lmpart a cont~inuou~ unidirectional movement of thé'tape'46 from the ~upply reeI 42'.onto the take-up reel 3o 44. The'rec'order 10 is -typically in contlnuous use'~or .j ~

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47,488 _9_ periods in the order of one month and the tape speed moves slowly, in the order seven inches (17.8 cm.) per hour. The capstan shaft 24 is rotated approximately one revolution, every 15 minutes ~or movement o~ 1.75 inchès (.4.4 cm.) of tape movement.
The supply spindle assembly 26 forming an impor-tant part o~ the tape transport assembly 20 includes a spindle shaft 58 positioned so as to be coaxially aligned along the axis 60 extending through the center of the supply reel 42 when mounted in the recorder 10. The lower end of the spindle shaft 58 is threaded so as to be secured.by nut 61 within a hole opening o~ the boktom plate 1.4. The upper end o~ the assembly 26 terminates at the pins 30 carried by a pin support disc 62 held in place at the upper end thereof by a retaining clip 64 for rotation about the upper end o~
the spindle shaft 58. The assembly 26 includes a magnetic brake 66 for maintaining a controlled and substantially constant tape tension in the tape 46 as it is ~ed ~rom the tape coil on th~ reel 42 to the pulling engagement between . ' 20 the pinch roller 48 and oapstan shaft 24. ' The magnetic brake 66 is also shown in the en-larged view o~ ~ig. 4 and includes a stationary part 68.
The stationary part 68 is permanently magnetized including a flat ring 6.9, that is magnetlzed with several magnetic polesf and a magnet support plate.~0 lntegrally atta¢hed by a suitable'adhes'ive to the bottom face o~ the magnetized ring 69. In one p.re~erred embodiment, the permanently .
magnet'i.zed ring 69 is formed o~ an Alnico 5 permanent magnet .
material oriented per'pendlcular to the diameter and having a 3o thicknes~ in the order of o.~6 inch (0.'4 cm.), an outer 47, 4~38 diameter in the order of 1.25. inch (3.18 cm.) and a center hole having a diameter of 0.625 inch (1.6 cm.). The magnet-ized ring 69 i8 magnetized with eight magnetic poles circum-ferentially spaced on the upper face of the ring 69 around the shaft 58. The common directlon o~ magnetization o~ the eight magnet'ic poles ls parallel with the axis 60.
. An enlarged diameter section 72 of the shaft 58 is .I disposed in the center opening of the ring 69. The lower part of shaft 58 extends through the center of the magnetic support plate 70 so that a lower annular shoulder of the j shaft porti.on 72 iS clamped against the support plate 70 : when the shaft 58 ls attached to the bottom.plate.14 by , means of the nut 61 threaded to the thread,ed end o~the ': shaft 58.
A rotational part 7ll of the magnetic brake 66 is formed by an annular permeable or soft magnetic plate (~ormed of a cold rolled steel material).that is integrally attached to the bottom o~ the pin suppork disc 62. It is to be understood that the permanent magnet material, such as ; 20 forming the rlng 69 has a high retentivity property so that residual magnetism therein remains substantially permanently.
The 80~t or permeable magnetic material used ~or the plates 70 and 74 has a low reluctance characterlstic whlle havlng a relatlvely low retentivity propert~. Holes in the cenkers of the' magnetic plate 74 and of the pin suppork disc 62 recéive the'upper end of khe spindle shaft 58. A spa¢er washe'r 78 is mounted on the'shaft :58 and in the non-magnetic air gap between the'magnet:i.zéd ring 69 and so~k magnetlc plate'74., The spacer washer is pre~erably made of a non-magnet'ic plastic ~ilm material sold under the' trademark 47348~

"Mylar" by Du Pont de Nemours, ~.I..and Company or the equivalent. The Mylar material is a polyethylene terephthal-ate composition which is strong and wear resistant, non-porous and dimensionally stable at high temperatures and further has substantially no magnetic characteristics. The spacer'washer 78 has a thlcknes's in the order o~ 0.01 inch (0.25 cm.) and has a outer diameter ln the order of 1.125 inch t2..9 cm.) and has a hole in the center thereof to receive'the' shaft 58 as shown in Figs. 2 and 3.
The spacer washer 78 spaces the lower face of the magnetic plate 74 and the' upper face of the permanent magne-tized ring 69 so as to control the gap space.therebetween.
The gap is referred to as an air gap to dis~tingulsh'from a low reluctance path, although the plastic washer 78 is ~
disposed therein. This provides an important advantage ln this inventi.on in that the non-magnetic or air gap through :~
which the magnetic fluxes pass between the magnetlc poles of the ring 69 and plate 74 is accurately controlled. Thus, the gap spacing is variable with different thicknesses of the washer. If the magnetic plate 74 rests on the upper shoulder of the enlarged sha~t section 72~ extremely close tolerances in manu~acturing must be maintained and as~embling of the parts,must be carefully controlled in order to maintain ~.
a controlled magnetic air gap space. The use o~ the spacer washer ellminates the very close eXaGtneSs ln these manufac-turing oper'atlons. A furthe'r highly advantageoùs feature of the spacer washe'r 7~ is that.the'~gap space.between the magnetizéd ring 69 and thb magnet'ic plate.74 is occupied by the washer 78 so that dust and magnet:ic particles are'not attract'e:d and co'llected the'rei'n to var~ the characteristics ,: ', "" , ' `' ' 47~48g ~12-of the magnetic brake operation and cause wear and damage to the relatively rotating parts of the magnetic brake 66. The spacer.washer 78 additionally provides a substantial.propor-tion o~ drag provided by the magnetic brake so that the ; overall size o~ the magnetized ring 69 may kept at a minimum to reduce the: cost and space:required for the supply spindle assembly 26.
- The magnetic brake 66 is assembled by first mag-netizing the ring 69 with plural magnetic poles. Then the integral part~ 69 and 70, washer,78 and lntegral parts 62 ., and 74 are assembled to the splndle sha~t 58. A test reel is engaged by the pins 30 and the torque required to rotate the tes't reel measured. The ring 69 is de~agnetlzed until the desired braking torque is ob-.tained. A calibrated torgue of 1.2 inch-ounces is provided to rotate the disc 62 against the drag force o~ the brake 66. Dlmensional changes in the gap spacing between the parts 74 and 69 can produce undesired results ~hereas use o~ the washer 78 closely.cantrols the gap so that it ls substantialIy constant.
The tape tenslon between the reel 42 and the capstan shaft increases slightly in.operation from a substan-tially ~ull reel so that the tension approxlmately doubles when the reel becomes empty of tape. It i~ belie~ed that the permanent magnet ~luxes from the rlng 69 induGe consequent or virtu&1 poles in the permeable magnetic plate 74. The resulting magnet'ic attractlon between the permanent magnet poles and ~irtual poles resists.,rotatlon of the'.plate '74.
The washer 78 produces an additional frictional ret'ardlng force''on the plate 74.: Th.usj the '.tension in tape 46 between the reel 42'and capstan shaft 24:is wlthln controlled low 3 47,4~,~

limits3 generally in an approximate range of two to ~our ounces; so as to be characterized as being substantially constant. It is to be recalled that the rotation of the reel 42 varies withln a relatively low range of speeds.
The take-up spindle assembly 28 shown in Flg. 2 is mounted'along the axis 8b including the center axis of the take-up reel 44 when the cartridge 38 is in the mounted and '~` ~ operatlve position shown in Fig. 2., A magnetic clutch 82 is included in the assembly 28 to rotate the reel 44 when it is engaged by the pins 32 so as to wind up the tape 46 into a coil thereon as the tape is ~ed ~rom the capstan shaft 24 and pinch roller 48. The speed is varled as the tape ll6 is wound on the reel so that it does not pull`the tape relative to the capstan nor allow access slack in the take-up tape , portion between the capstan and the coil on the reel 44.
As shown more clearly in Fig. 3, a spindle shaft 86 o~ the assembly 28 is mounted along the axis 80 and the -lower threaded end thereof recelves a nut 87 which holds the shaft 86 to the bottom plate 14. A bushing 88 supports the bottom of a pulley 90 on the bottom plate 14. The bushing 88 and the pulley 90 may be made o~ an integral part. A
groove in the pulley 90 receives a belt 92 mounted in a groove 93 at the lower end o~ the capstan sha~t 24 shown in Fig. 2. The beIt 92 is in non-slipping engagement with the groove 93 and the groove in the pulley 90.
A permanently mag~etized flat ring 94 is secured by a suitable adhesive to the pulley 90 and has a hole through the'center thereo~ ~ec'eiving the spindle shaft 86.
The magnet'ize'd'rlng 94 is made of a permanent magnet' mater-ial such''as that describe'd for the ring 69 and includes a , ~ .

47,il8-14-plurality, such as eight, magneti.c poles therein circumfer-entially disposed around the shaft 86. A stronger permanent magneti.zing material may be used in some instances rather than the type used for the ring 69 due to reduced space for the ring 94. ~he magnetlzed ring 94 forms the driving part of the magnetic clutch 82.
The drlven part of the magnetic clutch 82 includes a permeable or soft magneti.c plate 96 integrally attached to a pin support disc 98 corresponding to the pin support disc 62. In an alternative embodiment, the plate 96 is also formed of a permanent magnet' material having corresponding plural magnetic poles therein in a magnetically.attracting relationship with the magnetic poles of the`ring part 94.
The magnetic plate 96 is positioned above the magnetized ring 94 by a bearing washer or enlarged shaft section 100 o~
the shaft 86 so that a predetermined axial magnetic air gap is formed between the magnetlc poles of the magnetized ring 94 and magnetlc plate g6. The air gap space of the clutch optionally includes a Mylar spacer washer 102 formed to fit in the space between the magnetized ring .94 and magnetlc plate 96 to protect against aocumulation of dirt and magnet-ized particles in the magnetic coupling space between the parts 94 and 96.
The magnet~c:coupling between the driven part 96 and driving part 94 of the clutch 82 is also~believed due to the'attraction between~the consequent or virtual poles induce'd' in the plate 96 and the permanent:magnet poles of the'ring 9~. The'changes in rel'ati~e rotation or slippage are'due'to thb'ch'anges in the' diamet:er o~ the' tape on the reel 44,but ~n a controlled m?nner as established by the' ..

~ 2;~3 1~7~4~8 clutch 82..
In operation of the tape tran~port assembly 20, the supply reel 42 is considered to be lnitially filled with a coil.thereon of the tape 46 with the take-up reel 44 belng substantially empty of the tape 46. The motor 56 drives the capstan sha~t 24 through'the'gears 54 and 52 at the speed of one revolution per ~ifte.en minutes as noted hereinabove.
S~',,5~ The magnetic brake 66 produce's a drag on the reel 42 so that reslsting torque'is developed at.the reel 42 when the capstan 10 pulls the tape 46. As understood in the operation of tape recorders, the'supply reel 42.initially moves slower than the take-up reel 44 due to the differences in diameters o~
coils of the' tape 46 on the reels. Initial~ly, a minimum amount o~ sllppage and highest output speed relative to a constant lnput speed occurs at the magnetic clutch 82 of the take-up spindle assembly 28. Also, inltially, about three inches o~ tape is wound on the take-up reel 44 with each revolution thereo~ whereas approximately ten inches of tape is ~ed ~rom the reel 42.with each revolution thereof. As the tape 46 ls fed from the reel 42 to.reel 443 the opposite empty and filled reel conditions are reached wherein:approxi-mately three inches of tape wlll be fed from.the reel 42 with each revolution whlle approximately ten lnches will be placed on the reel 44 with each revolution. .Due to the increase'in diameter o~ the tape 46 on the ræel 44, controlled slippage'incr:eases at .the magnet'ic clutch 82.and th.e output speed dec'r'eases. Accordin~lyJ the magnetic c.lutch 82 ini-tially pro~ides approximatel:y one-half.rev'olution o~ the driven part :96. ~or each'capstan sha~t revoluti:on. At the end o~ the'tape 'take'-'up oper'ation, the''clutch'slip increases .. . . . . .

47,48 so that the driven part 96 rotates only about .twenty percent of a revolution relative'to: a complete rotation of the capstan sha~t. At the end of the winding operation,'the torque developed in the supply portion of the tape 46 between the reel' 42.and capstan 24 will change slightly to about twice the initial tension. As noted above, the reel 42 reaches its hi'ghest rotatlonal speed and the reel 44 reaches its slowest rotational spee'd when the tape coil on the reel 44 includes substantially all o~ the strip of tape 46 provlded in the cartridge 38. In typlcal operation the tape movement is continuous for a period of one month.
An alternative embodiment of a supply spindle assembly 108. is shown in Figs. 5 and 6 including an alter~
.native magnetic brake 110 havingla magnetlc coupling ad~us~-ment feature. The spindle shaft 58 is substantially as described in connection with the descriptlon of the supply spindle assembly 28. A soft magnetic plate 74 and integral pin support disc 62 with the pins 30 are also provided as described herein~bove ~or the assembly 26. A series of eight separate cylindri¢al permanent magnets 113, 114, 115, 116, 117, 118g llg, and 120 are slidably mounted.on a so~t : or permeable magnetic support plate 121 to de~ine eight sepa~ate magnetic poles of the stationary.part of the magnet~c brake'llO. The permanent magnets are mounted in slots 122, 123, 124,. 125, 126, 127, 128 and 129 extending through both the magnet support plate 121 and the bottom plate.14.
Screws' 132'.éxtending through the''slots cla~p the permanent magnet's.ln adJu~table radial positions relative to:the ce'nter'axis 60'o~ the'supply splndle ~ssembIy 108 when arranged as is the' assembl'y 26. in ~he recorder. Accordingly, 47,4~8 a variable drag torque can be ad~usted by the positioning of the separate permanent magnets.113 through 119 relative to different radial positions of the magnetic plate 74. Fewer than all eight of the separate permanent magnets, such as alternate permanent magnets.113, 115, 117 and 119, may be mounted in slots so that they can be ad~usted to provide a desired reel drag ad~ustment to produce a desired drag ... . during the tape playout operation of the assembly 108. The non-magnetic plastic spacer washer 78 is provided between the faces of the permanent magnets designated 113 through 1 120 and the bottom surface of the magnetic plate 74 as :: provided in the assembly 26. Thus, the washer 7a provides the air gap spacing and protection o~ the magnetic air gap from debris and magnetic parti.clesO As noted rOr the spacer washer 78 hereinabove, ad~usting of the thickness o~ the washer is a further means of ad~ustlng the magnetic gap between permanent magnets and the plate 74 to ad~ust the retarding torque or magnetlc drag produced by the magnetic brake 110.. The washer 78 also produces additional frictional retarding force as the plate 74 is rotated thereon.
While preferred embodiments of the presenk lnven-tion have been described hereinabove, it is to be understood that obvious modifications and alterations thereof may be made by those skilled in the art without depar~ing from the spirit and scope of the following claims. - :.

Claims (8)

47,488 I claim:

1. A tape recorder device having a tape transport assembly for continuously moving a recording tape between supply and take-up reels, comprising:
a capstan assembly including a capstan shaft having an upper end for drivingly engaging the recording tape, and a drive motor having a direct drive engagement with a lower end of said capstan shaft;
a supply spindle assembly including a spindle shaft carrying a supply reel engaging member at the upper end thereof and a magnetic brake arrangement mounted about a lower portion of said shaft, said magnetic brake arrangement including axially spaced stationary and rotatable parts, one of said parts being formed of a permanent magnet material and including a plurality of circumferentially spaced magnetic poles and the other of said parts being a plate of a permeable magnetic material, and said supply spindle assembly further including a non-magnetic spacer washer made of plastic film material supporting said rotating part on said stationary part such that the axial spacing of said parts is determined by the thickness of said washer and retarding forces are produced by both the frictional engagement between said washer and said rotating part and magnetic coupling between said stationary and rotating parts; and a take-up spindle assembly including a spindle shift carrying a take-up reel engaging member at the upper end thereof and a clutch arrangement mounted about a lower portion of said spindle shaft, said clutch arrangement including driving and driven parts with said driven part being connected in continuously drlven relatlonship with the 47,488 lower end of said capstan shaft.

2. A tape recorder device as claimed in claim 1 wherein said magnetic brake arrangement includes a spacer washer made of a Mylar plastic film material.

3. A tape recorder device as claimed in claim 1 wherein said supply spindle assembly includes said shaft carrying an enlarged diameter section, and wherein said magnetic brake arrangement has the stationary part thereof formed by the permanent magnet material having a flat ring configuration with a magnet support plate made of a permeable magnetic material and integrally attached to the flat ring of permanent magnet material, and further wherein a lower shoulder of the enlarged diameter section engages said magnet support plate to secure said stationary part in said recorder device.

4. A tape recorder device as claimed in claim 3 wherein said supply reel engaging member has integrally attached thereto said plate of permeable magnetic material forming said rotatable part of said magnet brake arrangement.

5. A tape recorder device as claimed in claim 4 wherein said enlarged diameter section of the supply spindle shaft has a length not greater than the height of the per-manent magnet flat ring with said spacer washer extending over an upper shoulder of said enlarged diameter section.

6. The tape recorder device as claimed in claim 4 wherein said supply reel engaging member includes at least one pin engageable with said supply reel and a disc member supporting said at least one pin so that the pin extends from the top thereof with said disc member further carrying the permeable magnetic plate on the bottom thereof.

47,488

7. A tape recorder device as claimed in claim 1 wherein said clutch arrangement of said take-up spindle assembly includes a magnetic clutch having one of said driv-ing and driven parts being axially spaced and the other of the parts and formed of a permanent magnet material and further having the other of said driving and driven parts formed of a permeable magnetic material so that the driven part is magnetically coupled for variable rotation in response to rotation of said driving part.

8. A tape recorder device as claimed in claim 7 wherein said magnetic clutch includes a non-magnetic plastic spacer washer disposed in the axial space between said driving and driven parts thereof.